In the art of glass making, comparatively few glass compositions are known which exhibit linear coefficients of thermal expansion and contraction in the low to medium expansion and contraction range of from about 4 .times. 10.sup.-.sup.7 to 20 .times. 10.sup.-.sup.7 in./in./.degree.C. over the temperature range from 0.degree. to 300.degree.C. Moreover, such glass compositions as are known to exhibit desired low to medium expansion and contraction properties characteristically have been produced either from glass batch compositions which require the employment of exceedingly high glass batch melting temperatures or from glass batch compositions which are unsuitable for conventional glass batch melting techniques and require resort to expensive and complicated processing techniques such as vapor phase reactions. In either instance, however, production capabilities are so extremely limited and processing costs are so expensive that such previously known glass compositions generally have been regarded as being outside the realm of practicability for commercial production of moderate cost glasses and, in consequence, practical commercial applications of such glasses have been quite limited.